Application of expert system techniques to fault diagnosis

Abstract

An expert system, as viewed in the context of this paper, consists of inference algorithms which manipulate a knowledge database created by subject experts. In a fault diagnosis application, if-then production rules can be used to organize the expert knowledge regarding fault isolation. The process of successive classification of system states can be formulated by the following form of the rule: if [system state i] and (observable fact) then [system state j] For example, if [pump flow is low] and (low pressure exists at the suction valve) then [suction valve is closed] The example provided, which involves an application to an engine cooling system, has 22 if-then rules for cause isolation. The inference algorithm used in the interactive conversation with the operator informs him of (1) the if-then rule currently being applied, (2) the proven states and facts in the prerequisite of the rule and (3) a conclusion when the observable fact about which the computer asks turns out to be true.